A theory for molecular transport phenomena through thin membranes

Theory for molecular transport phenomena through thin membrane

Oxygen in the Galactic thin and thick disks

First results from a study into the abundance trends of oxygen in the Galactic thin and thick disks are presented. Oxygen abundances for 21 thick disk and 42 thin disk F and G dwarf stars based on very high resolution spectra (R\sim 215000) and high signal-to-noise (S/N>400) of the faint forbidden oxygen line at 6300 A have been determined. We find that [O/Fe] for the thick disk stars show a turn-down, i.e. the ``knee'', at [Fe/H] between -0.4 and -0.3 dex indicating the onset of SNe type Ia. The thin disk stars on the other hand show a shallow decrease going from [Fe/H] \sim -0.7 to the highest metallicities with no apparent ``knee'' present indicating a slower star formation history.Comment: To be published in "CNO in the Universe", ASP Conference Series, C. Charbonnel, D. Schaerer & G. Meynet (eds.

Dynamics of Charge Leakage From Self-assembled CdTe Quantum Dots

We study the leakage dynamics of charge stored in an ensemble of CdTe quantum dots embedded in a field-effect structure. Optically excited electrons are stored and read out by a proper time sequence of bias pulses. We monitor the dynamics of electron loss and find that the rate of the leakage is strongly dependent on time, which we attribute to an optically generated electric field related to the stored charge. A rate equation model quantitatively reproduces the results.Comment: 4 pages, submitted to Applied Physics Letter

Some Effects of Roll Rate on the Longitudinal Stability Characteristics of a Cruciform Missile Configuration as Determined from Flight Test for a Mach Number Range of 1.1. to 1.8

A model of a cruciform missile configuration having a low-aspect-ratio wing equipped with flap-type controls was flight tested in order to determine stability and control characteristics while rolling at about 5 radians per second. Comparison is made with results from a similar model which rolled at a much lower rate. Results showed that, if the ratio of roll rate to natural circular frequency in pitch is not greater than about 0.3, the motion following a step disturbance in pitch essentially remains in a plane in space. The slope of normal- force coefficient against angle of attack C(sub N(sub alpha)) was the same as for the slowly rolling model at 0 degrees control deflection but C(sub N(sub alpha)) was much higher for the faster rolling model at about 5 degrees control deflection. The slope of pitching-moment coefficient against angle of attack C(sub m(sub alpha)) as determined from the model period of oscillation was the same for both models at 0 degrees control deflection but was lower for the faster rolling model at about 5 degrees control deflection. Damping data for the faster rolling model showed considerably more scatter than for the slowly rolling model

FISH1D 2.2 User’s Manual

FISH1D is a computer program that solves the one-dimensional Poisson equation for electrostatic Fields in Semiconductor Heterostructures. The program will print or plot the electrostatic potential, electric field, electron and hole densities, dopant density, ionized dopant density, and other quantities of interest versus position at an applied bias voltage (assuming zero current). A capacitance or sheet carrier concentration versus voltage analysis may also be performed. While FISH1D was originally written for the ternary Alx Ga1 _xAs, it has been modified to simulate CdxHg1^xTe, ZnSe, GexSi1^ , and Si as well, and the program can be readily modified to analyze other semiconductors through the addition of new material subroutines or using the most recent option, the MATDEF card. This card enables the user to enter new material definitions by layers in the input deck without having to recompile, an advantage of FISHlD 2.1 over FISH1D 2.0. Simulations of bipolar transistors under bias are now possible in FISH1D 2.2, which has an upgraded BIAS card. The primary purpose of this document is explain how to use FISH1D; for a more thorough discussion of the numerical implementation of FISH1D, the user is directed to the references. A theoretical basis for FISH1D is provided in Appendix I of this manual

Electrical characteristics of nearly relaxed InAs/GaP heterojunctions

The electrical properties of lattice mismatched InAs/GaP heterojunctions are examined. In spite of a high dislocation density at the heterointerface, the current versus voltage characteristics show nearly ideal behavior with low reverse leakage currents and high breakdown voltages. The forward currentvaried exponentially with bias displaying ideal factors of 1.10 or less. Band offsets estimated from current–voltage and capacitance–voltage analysis are consistent with previous estimates based on differences in Schottky barrier heights

A Theoretical Investigation of Surface Roughness Scattering in Silicon Nanowire Transistors

In this letter, we report a three-dimensional (3D) quantum mechanical simulation to investigate the effects of surface roughness scattering (SRS) on the device characteristics of Si nanowire transistors (SNWTs). We treat the microscopic structure of the Si/SiO2 interface roughness directly by using a 3D finite element technique. The results show that 1) SRS reduces the electron density of states in the channel, which increases the SNWT threshold voltage, and 2) the SRS in SNWTs becomes more effective when more propagating modes are occupied, which implies that SRS is more important in planar metal-oxide-semiconductor field-effect-transistors with many transverse modes occupied than in small-diameter SNWTs with few modes conducting.Comment: 13 pages, 4 figure

Transonic-flutter Investigation of Wings Attached to Two Low-acceleration Rocket-propelled Vehicles

Two low-acceleration transonic-flutter vehicles were launched and flown. The first carried two test wings, one of which fluttered at M = 0.92 at a frequency of 61.4 cycles per second. The reference flutter speed determined from two-dimensional theory for an unswept wing in incompressible flow is conservative when compared to the experimental flutter speed. The second vehicle carried two test wings, one of which failed at M = 0.71 because of low-frequency divergent oscillation. Since this failure was not caused by conventional flexure-torsion flutter, no comparison with a reference flutter speed can be made